1. Field of the Invention
The present invention relates to a two-layer optical disk having two recording layers to which information is recorded, and enabling information on both recording layers to be reproduced by irradiating the disk with light from only one recording layer side.
2. Description of the Prior Art
Optical disks having two data recording layers ("two-layer optical disks" below) from which data can be reproduced by irradiating the disk with light from one side of the disk have been developed and described in U.S. Pat. No. 5,428,597.
The structure of a two-layer optical disk is shown in FIG. 11. As shown in FIG. 11, this two-layer optical disk comprises a first recording layer 1102 and a second recording layer 1104 disposed between a bottom resin base 1101 and a top resin base 1105 with a resin bonding layer 1103 disposed between the two recording layers. Data bits 1126 are recorded to the first and second recording layers in spiral or concentric recording tracks. Note that the data bits 1126 may be formed as physical pits and lands, or as amorphous bits. Note also that the first recording layer 1102 is semi-transparent.
When reading this two-layer optical disk, light is emitted to the disk from only one side thereof, i.e., the side to which the resin base 1101 is disposed in this example. The data recorded to the first recording layer 1102 can thus be read by focusing the emitted light on the first recording layer 1102. Because the first recording layer 1102 is transparent, data on the second recording layer 1104 can be read by focusing the light on the second recording layer 1104 through the first recording layer 1102.
Applications for a two-layer optical disk include using both first and second recording layers to record movies and other types of extended, continuous information, and using the first recording layer to record first information (such as a directory) and the second recording layer to record plural data referenced by the first information.
There has been proposed no system or method for sequentially recording and reading the data on the two-layer optical disk.